Few researchers have addressed the important issue of three-dimensional multiple object selection (MOS) in immersive Virtual Environments (VEs). We have developed a taxonomy of the MOS task as a framework for exploring the design space of these techniques. In this thesis, we describe four techniques for selecting multiple objects in immersive VEs. Of the four techniques, two are serial (where only one object can be indicated per operation), and two are parallel (where one or more objects may be indicated per operation). Within each of the two categories we also investigated two metaphors of interaction: a 3D spatial metaphor and the pen and tablet metaphor. Two usability studies were used to evaluate the four techniques, iterate their designs, and gain a deeper understanding of the design space of MOS techniques. The results from our studies show that parallel MOS techniques can select objects faster than serial techniques as the number of target objects increase. We also show that effective techniques for MOS in immersive VEs can be created using both pen and tablet and 3D metaphors.